html,body {
  margin: 0;
  background-color: #eee;
  height: 100%;
}

h1 {
  text-align: center;
  margin: 0;
}

#contentbox {
  margin: 0 auto;
  width: 500px;
}

#circuit {
  background-color: white;
  width: 100%;
  height: 350px;
  border: 1px solid black;
}

#credits {
  width: 500px;
  margin: 0 auto;
  text-align: right;
  font-family: sans-serif;
  font-size: small;
}